Relative thickness. (Thickness x 10000: length.) 
HYALONEMA (OONEMA) BIANCHORATUM PINULINA. 
317 
upper part of the stalk imbedded in the sponge-body are not centrotyle am- 
phioxes. The largest one observed was 7 mm. long. 
The acanthophores (Plate 83, figs. 1-35) are normally composed of one 
to six rays. One quite abnormal one (Plate 82, fig. 24), which I found in speci- 
men a, has two long and six more or less reduced rays. 
O cn o cn 
Number of 
thickness. 
spicules of this relative 
Fig. 18. — Amphioxes. 
